1. Field of the Invention
The invention relates to a surface area vacuum gripper for suctioning and manipulating workpieces, including a housing having a vacuum chamber that can be subjected to a vacuum. The housing has suction openings on its suction surface facing the workpiece, having a suction cross-section, wherein a flexible lining is allocated to this suction surface, which is placed on the workpiece.
2. Description of the Related Art
Surface area vacuum grippers of this type serve, in particular, for gripping and lifting objects by layers, such as flat materials that can be stacked in layers, e.g. boards or sheets, or smaller objects, e.g. cans, cups, bowls or suchlike. The surface area vacuum gripper has a flexible lining, which is normally placed on the upper surface of the object that is to be gripped. A foam rubber lining has proven to be advantageous, because this material adapts well to potentially uneven surfaces. There is still, nevertheless, the problem that different objects have different surfaces, and there may also be large gaps between the objects. In particular food cans or drink cans have an edge that protrudes upward. The available suction surface area is reduced because of this edge, as a result of which, a lifting of the object can only be implemented with an increased suction force. It is further problematic when different objects are to be gripped that have different heights, edges extending axially, or other contours such as pull tabs on cans.
The flow behavior of the surface area vacuum gripper must thus be adjusted precisely to the object that is to be gripped. For this reason, the foam rubber lining in conventional surface area vacuum grippers is provided with a cover layer having suction openings, the flow cross-sections of which are adapted precisely to the object that is to be gripped. One example of a surface area vacuum gripper is disclosed in published German Application No. DE 10 2006 050 970 A1.
With other surface area vacuum grippers, the suction openings are provided with flow control valves, which close those openings that are not occupied, such that the flow losses can be kept low.
If a surface area vacuum gripper is to be used for other objects after completing a work process, this gripper must be adjusted for each change to the other objects in that the flow cross-sections and/or the flow resistances must be changed, or flow control valves must be added or removed. This not only takes time, but is also cumbersome and may lead to malfunctions.
Another example of a surface area vacuum gripper is disclosed in published German Application No. DE 10 2006 012 895 A1, which has a suction plate having numerous suction openings, which can be modified or adjusted by a slider mounted on the interior of the housing. In this representative example, however, the housing must be opened, which may not be desirable, or may not be possible, e.g., due to a lack of tools. Other examples of surface area vacuum grippers having a layered type construction of numerous flat components, such as suction plates and hole templates, are generally disclosed in published U.S. Application No. US 2003/0164620 A1, published German Application Nos. DE 100 09 108 A1, DE 196 46 186 A1, published European Application No. EP 0 267 874 A1, published German Application Nos. DE 30 47 717 A1, and DE 20 2012 000627 U1.